Implants for use in fusing adjacent bony structures facilitate fusion by maintaining the adjacent bony structures in a predetermined spaced relationship while bone grows between them. In some cases these implants are formed from body tissues. In forming an implant from body tissue, a source of tissue, such as a bone, is formed into pieces meeting the desired shape and strength requirements for a particular implant. In the case of bone, the requirements are often specified in terms of a minimum wall thickness, minimum load bearing capacity, and/or geometric size and shape. A portion of the source tissue, including pieces removed in forming implants, will fall short of the requirements to form an integral implant. Thus, it is often difficult to obtain a high yield from a particular source.